32 results about "Spatial fourier transform" patented technology

An estimated frequency-wavenumber spectrum is generated by applying a first Anti-leakage Fourier transform method to unaliased frequency components in temporal-transformed seismic data and applying a second Anti-leakage Fourier transform method to aliased frequency components in the temporal-transformed seismic data. The second Anti-leakage Fourier transform method applies an absolute frequency-wavenumber spectrum extrapolated from unaliased frequencies to aliased frequencies to weight frequency-wavenumber components of the aliased frequencies. An inverse temporal and spatial Fourier transform is applied to the estimated frequency-wavenumber spectrum, generating trace interpolation of the seismic data.

In an inspection system for planar objects having periodic structures, programmable optical Fourier filtering in the focal plane of a telecentric lens system is used to directly identify physical phenomena indicative of non-periodic defects. Lens assemblies and a coherent optical source are used to generate and observe a spatial Fourier transform of a periodic structure in the Fourier plane. Optical Fourier filtering (OFF) is performed in the focal plane using an electrically programmable and electrically alignable spatial light modulator. The spatial light modulator with high signal to noise ratio is electrically reconfigurable according to a feedback-driven, filter construction and alignment algorithm. The OFF enhances any non-periodic components present in the Fourier plane and final image plane of the object. A system having a plurality of inspection channels provides high-throughput inspection of objects with small non-periodic defects while maintaining high detection sensitivity.

A system for producing an image using an imaging system includes a) transmitting at least one signal of energy toward an object to be imaged by using two transmitters having the same output amplitude but of an opposite sign, or by using one transmitter to perform the task; b) exciting at least one transducer element to produce limited-diffraction array beams or their square-wave approximations with two levels of quantitations for both sine and cosine functions, c) weighting the received signals spatially with limited-diffraction array beams, their square-wave approximations, or spatial Fourier transform, and d) digitizing and then transferring received signals through high-speed optical fibers to a system for image reconstructions.

Methods and apparatus for method for characterizing a height profile of a scattering surface relative to a fiducial plane. The scattering surface, which may be an interface between distinct solid, liquid, gaseous or plasma phases, is illuminated with substantially spatially coherent light, and light scattered by the scattering surface is collected and dispersed, such as by a grating, into zeroth- and first-order beams. A spatial Fourier transform of the zeroth- and first-order beams is created, and one of the beams is low-pass filtered. The beams are interfered at a focal plane detector to generate an interferogram, which is transformed to retrieve a spatially resolved quantitative phase image and / or an amplitude image of the scattering surface. Imaging may be performed during an etching process, and may be used to adaptively control a photoetching process in a feedback loop.

The invention provides a compressor stall pre-warning signal reconstruction and identification method based on a single-path sensor signal. The method includes obtaining the pressure signal through asingle-path sensor installed in the circumferential direction of a front-stage case of a compressor; and then according to the rotation characteristic of the compressor stall pre-warning signal, simulating the output of a multi-path sensor in the circumferential direction by adopting a signal translation method, and realizing the multi-path stall pre-warning signal reconstruction of the compressor. The reconstructed multi-path stall pre-warning signal is expressed as the superposition of the torus average and the circumferential pressure disturbance in the vector form, and the circumferentialpressure disturbance vector is subjected to the spatial Fourier transform to be decomposed into the superposition of multi-order modal waves; the first-order modal amplitude is compared with the set threshold value, and the stall is considered to occur when the threshold value is exceeded, and the identification of the stall pre-warning signal is realized. A single sensor can be used to replace aplurality of sensors, so that the defect that a plurality of sensors are installed is overcome, and the method has a large engineering application value.

The invention discloses a method for obtaining dispersion characteristics and coupling impedance of slow-wave structures. Firstly, a lossless slow-wave structure model to be processed is established, and relevant parameters of the slow-wave structure model are set, and then sinusoidal excitation signals are input. t after energy stabilization of the wave structure model 0 At time, the time-domain field monitor extracts the electric field distribution on the field monitoring line to obtain the electric field map, and then performs spatial Fourier transformation on the electric field map, and performs parameter correction, and finally calculates the dispersion characteristics and coupling impedance of the slow wave structure.

The invention provides a directional modulation signal design method based on spatial Fourier transformation. The method comprises the following steps of establishing desired phase wave beam spatial coverage functions in ideal conditions relative to different communication models; and acquiring a phased array element weighted value according to the spatial Fourier transformation pair relation among phase wave beams and the array element weighted value of a phased array in a directional modulation signal transmitter to achieve a directional modulation signal design in different communication models. By using the directional modulation signals designed by the method, valid users can normally demodulate received directional modulation signals through common digital signal receivers. As to wiretappers in undesirable directions, their wiretapping receivers cannot demodulate useful communication information from received signals due to the relative phase relationship distortion of constellation points in a received signal constellation diagram. The invention provides a safe transmission method for transmitting communication information in wireless channels.

The invention discloses an acoustic tweezers realization method and system based on spatial Fourier transform, and belongs to the technical field of acoustic manipulation. Aiming at the problem that in the single-frequency standing wave acoustic tweezers existing in the prior art, an acoustic radiation potential well distribution that can be defined arbitrarily cannot be formed in space, so that multiple target objects cannot be independently manipulated, the present invention provides a spatial Fourier-based The acoustic tweezers implementation method and system of leaf transformation, using the orthogonality of trigonometric functions, decomposes the acoustic radiation potential distribution expected to be formed in the space domain into the superposition of the acoustic radiation potential on multiple frequency components, and the amplitude of the obtained components The sum and phase determine the electrical signals used to drive the two transducers; the frequency components of the acoustic radiation potential are adjusted based on the control requirements to realize the dynamic adjustment of multiple independent acoustic radiation potential wells. It overcomes the deficiency that the existing single-frequency standing wave acoustic tweezers cannot independently control multiple target objects, and greatly improves the flexibility of the acoustic tweezers.

The invention discloses a broadband target detection method in a complex environment with strong interference. The method includes: receiving a time-domain array signal collected by a uniform line array, and dividing the time-domain signal of each channel into a plurality of subbands through Fourier transform , obtain the signal matrix in the array element domain-frequency domain; the signal matrix in the array element domain-frequency domain is filled with zeros in the array element dimension, and converted to the frequency domain-wavenumber domain through the spatial Fourier transform; the main lobe discrimination method is designed to identify different targets for the same target. The main lobe of the wavenumber spectrum at the frequency; the main lobe allocation rule is designed to realize the allocation of all main lobes on the full-band wave number spectrum; the azimuth is formed by the mutual weighting of the main lobe energy accumulation and main lobe number accumulation in the processing frequency band spectrum, so as to achieve broadband target detection. The method of the invention has the advantages of effectively detecting weak targets in a complex environment with multiple targets and strong interference, and has both stability and reliability.